Conventionally, there is known a robot system that conveys a substrate, such as a wafer, into or out of a processing apparatus in a semiconductor manufacturing process by using a robot, such as a horizontally articulated robot.
In such a robot system, the importance of safely and reliably conveying a substrate has been increasing with the increase in the size and cost of substrates, which are the objects to be conveyed. Therefore, recently, various technologies for safely and reliably conveying a substrate have been proposed.
For example, Japanese Patent Laid-open Publication 2011-159738 discloses a technology for preventing displacement and the like of a substrate during conveying by providing a robots' hand, which is for placing a substrate, with a gripping mechanism.
In the technology described in Japanese Patent Laid-open Publication 2011-159738, in order to reliably grip a substrate by the gripping mechanism, the robot is temporarily stopped after the robot receives the substrate from a processing apparatus and then the gripping mechanism is operated. Moreover, in the technology described in Japanese Patent Laid-open Publication 2011-159738, the presence or absence of the substrate is confirmed based on the operating state of the gripping mechanism after operating the gripping mechanism and, after it is confirmed that the substrate is present on the hand, the robot is operated again to retract the hand.
However, in the technology described in Japanese Patent Laid-open Publication 2011-159738, the gripping operation and the presence/absence confirmation of the substrate are performed independently of the retracting operation of the hand. In other words, in the technology described in Japanese Patent Laid-open Publication 2011-159738, the retracting operation of the hand is not performed while the gripping operation and the presence/absence confirmation of the substrate are performed, therefore, the time required to convey the substrate may become long.